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Author Topic: GML Moving Faders jumping  (Read 1924 times)

steve p

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GML Moving Faders jumping
« on: June 27, 2006, 10:28:41 PM »

I have an Amek APC 1000 desk that i have installed in my new room,

When i make moves and play them back the faders are Jittering...

Maybe a 1/4 inch or less from the center point of the desired position, when they are moving.

Does anyone have any experience with this  ???


They all do it not just a few,

once they come to rest at the desired position they are fine and stop jittering.

could this be transistors on the fader buffer cards ?

caps on the fader cards ?

or.......




Thanks in advance,


steve



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Steve Perkins


Creation Recording Studios

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JOHN 3:16

Jolly Ted

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Re: GML Moving Faders jumping
« Reply #1 on: June 29, 2006, 04:28:48 PM »

Hi Steve,

What condition is your fader PSU in? Check the voltage, regulation and scope it out for noise on the DC rails. I have seen this behavior before with a failing PSU driving the fader motors and the electronics.

regards,

Ted Jolly
GRS Systems
http://www.grssystems.com

steve p

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Re: GML Moving Faders jumping
« Reply #2 on: June 30, 2006, 02:55:38 AM »

Hi TEd,

Thanks for the reply,

The PSU is in good shape with voltage stable and no AC Present on the DC rails,

I just mixed a project tonight and noticed some faders Jitter more than others and only on slow moves,

On fast moves there smooth and accurate.


I recapped the fader buffer cards earlier ,

Do you think the Transistors on the buffer cards could be the problem ?

Also there are some Huge filter  Caps in the PSU ( Coke can size )

One of these had a leak,  I have them on order now .......

Do you think the filter caps could cause this Jittering?




Thank you,


steve







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Steve Perkins


Creation Recording Studios

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JOHN 3:16

Jolly Ted

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Re: GML Moving Faders jumping
« Reply #3 on: June 30, 2006, 07:08:39 PM »


Double check the DC rails suppliying the fader electronics. Look for AC noise / hash in the milivolt range.

We had to put snubbers on several Amek PSU's to cure a similar problem AFTER the problem still existed after a complete filter cap re-cap. The noise was playing havoc with the GML fader boards.

If this is happening to ALL faders, I doubt that it is related to every board having a bad transistor...but anything is possible. I would first verify your PSU for noise, then scope the signal lines to the fader boards. A schemo would help me guide you since my memory of the GML fader boards is fuzzy.

Leaky PSU filter caps are not good. Good you're replacing it. Do your testing after installing the new cap(s).

Do you have a schematic you can share? Having worked on many, many Amek's...I don't have a schemo of GML fader circuits in my possesion for your board. And as you know, yours is a very rare board.

Regards,

Ted Jolly
GRS Systems, LLC
http://www.grssystems.com

Dave Hecht

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Re: GML Moving Faders jumping
« Reply #4 on: July 01, 2006, 04:31:34 AM »

Steve,

 I agree with Ted that you should double check your DC rails on the fader supply. I also doubt you have bad transistors across all the fader cards.

 Another thing to look at is the ribbon cables from the computer to the card cage(s). Make sure they are all seated well, and look for any frayed or damaged cables.

 Also, the ribbon cables should be as short as possible. I spoke to George Massenberg about various fader problems years ago, and he was adamant about not exceeding the recommended cable length ( unfortunately, I can't remember the maximum length). GML will probably be able to give you that info if it's not in the manual.

 If it's not psu or cable related, you can try cleaning several faders to see if that makes any improvement. Although it's not likely, I have worked on a couple of GML systems where the faders hadn't been cleaned and lubed in so long that all the faders felt a bit sticky, so it is a possibility.

Dave Hecht
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Sahib

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Re: GML Moving Faders jumping
« Reply #5 on: July 01, 2006, 10:42:03 AM »


If they are all jittering this generally means that there is a global problem. I too would ask you to check your power supply first as the source of the noise.

However, if one or more faders have sticky mechanics then they will draw much larger start current and this would put noise back on the power rails too.

Cemal

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steve p

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Re: GML Moving Faders jumping
« Reply #6 on: July 01, 2006, 10:14:26 PM »

Thank you all for the replies and help,

I will replace the large filter caps , and check again for AC on the DC rails,

I have all the schematics for the desk, faders, ect.. but i don't think i have them for the buffer cards or the switch read cards,

cable length is around 25 ft and that is what is recommended from GML

i don't know how anyone could have it any closer..... (fan noise)

If the PSUs arnt the problem i will move the computer closer and test it with shorter cables

Thanks again, you guys are great !

Happy 4th  !!!



steve
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Steve Perkins


Creation Recording Studios

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JOHN 3:16

Rail Jon Rogut

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Re: GML Moving Faders jumping
« Reply #7 on: July 06, 2006, 02:35:13 AM »

The schematics should be in the back of the manual (check out the GML web site).

Rail
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Engineered Drums for BFD & Superior Drummer 2.0

steve p

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Re: GML Moving Faders jumping
« Reply #8 on: July 06, 2006, 04:20:33 AM »

I  tried to get them from the GML site.....

I dont thing that george wants anything to do with this old system... Crying or Very Sad



I have the fader schematics, but i would love to get the rest of the systems schematics.

I guess i should just call them.......


The filter caps should be here at the end of this week


I was doing a mix last night and useing the group master faders,
when i grouped several faders and did moves with the master they acted the same as when they were reading from disk

Looking at them on a slow fadeout they would move down 1/8" then up 1/8" then down and so on.....

But on fast moves they are fine....


Im starting to wonder if there is any calibration step i am missing in the GML system
(to easy)


One thing at a time, i will replace the filter caps first,
Already replaced the - side of the PSU and the + side checks out fine.

I cant realy shorten the cables any,..... the VME is way to loud to be in the same room as the desk.



steve
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Steve Perkins


Creation Recording Studios

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JOHN 3:16

Rail Jon Rogut

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Re: GML Moving Faders jumping
« Reply #9 on: July 06, 2006, 02:38:41 PM »

I spoke with George yesterday about a problem I was having with a GML Mac based system...  more of a Mac issue than GML.  He sent me a link to the latest manual.  If you need it email me.

Rail
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www.platinumsamples.com

Engineered Drums for BFD & Superior Drummer 2.0

steve p

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Re: GML Moving Faders jumping
« Reply #10 on: July 07, 2006, 02:22:01 AM »

I found the problem with the faders jittering...

It was a 74LS645N Chip on the small Buffer card that plugs into the Ribbon cable going to the VME.

Yea !! Very Happy


Still going to recap the filter caps in the PSU
so glad i didn't have to move the computer.



Thanks to all who replied  Smile



steve
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Steve Perkins


Creation Recording Studios

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JOHN 3:16
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